As shown in FIGS. 1 and 2, a prior art screwdriver comprises a plastic handle 1 and a shank 4. The handle 1 is provided at one end with a fastening hole 3 which is in turn provided with a plurality of retaining slots 2. The shank 4 is provided in the outer surface with a plurality of retaining projections 5 and is fastened with the handle 1 such that the retaining projections 5 are retained in the retaining slots 2 of the fastening hole 3. This prior art screwdriver is not effective in driving a badly rusted screw due to the lack of a percussion mechanism. In addition, the plastic handle 1 is not adapted to impact which is intended to help drive the badly rusted screw.
As shown in FIGS. 3 and 4, a prior art screwdriver comprises a handle 6 and a blade 10. The handle 6 is provided at a head end thereof with a metal body 7 which is provided at a fastening end 8 with a fastening hole 9 for fastening one end of the blade 10. The metal body 7 is used for percussion purpose in the event that the prior art screwdriver encounters with difficulty in driving a badly rusted screw. However, the metal body 7 is not an effective percussion mechanism.
As shown in FIGS. 5 and 6, a prior art screwdriver comprises a handle 11 and a tool head 15. The handle 11 is made of metal by machining. The tool head 15 is fastened at one end with a fastening end of the handle 11 in conjunction with a compression spring 14 which is located in a locating hole 12 of the fastening end of the handle 11. A locating pin 16 is used to locate the tool head 15 such that the locating pin 16 is retained in a retaining through hole 17 of the tool head 15 and one of the two V-shaped slots 13. When the handle 11 is impacted, the spring 14 is compressed by a reaction force of the tool head 15. In the meantime, the pin 16 moves downwards to arrive at the bottom point of the V-shaped slot 13. Subsequently, the pin 16 is caused by the spring force of the spring 14 to displace upwards, as shown in FIG. 7. Such a movement of the pin 16 along the V-shaped path brings about a rotating effect on a screw to be driven. In light of the handle 11 being made of metal, the prior art screwdriver is rather heavy and can not be easily maneuvered.